Circuit controlling device



Y May 7, 1940. T. LINDSTROM 2.199.641

CIRCUIT CONTROLLING DEVICE Filed Feb. 5, 1937 2 Sheets-Sheet 1 Insulation Insulation 11; i l l I l l WITNESSES; Z Z. INVENTOR m 7 Tame Lz'fidstrom.

y 1940- T. LINDSTROM I I 2.199.641

CIRCUIT CONTROLLING DEVICE 'Filed Feb. 5, 1957 2 Sheets-Sheet 2 A97 VII Farce Farce INVENTOR Tare L 2774 547 0772.

I BY fiz'szance 215x477 7/ 7. K 3 ATTORNQ? Patented May 7, 1940 PATENT QFFICE CIRCUIT CONTROLLING DEVICE Ture Lindstrom, Edgewood, Pa.., assignor to West-- inghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsyl- Vania Application February 5,

13 Claims.

My invention relates to electrical control de vices in general, and more particularly to trip devices for circuit breakers.

The usual forms of trip devicesthat have heretofore been used inconnection with circuit breakers have consistedin general of a movable latch and/or trip bar for normally restraining the spring biased contact opening or actuating member of the circuit breaker, and an armature biasecl to a normal position and movable to an attracted position by an abnormal condition responsive, electromagnet for moving the latch and /or trip bar to a tripping position to release the actuating member.

In moderate and large size circuit breakers, considerable force is required to trip the breakers and the spring means for biasing the armature to its normal or inoperative position exerts a relatively large force on the armature opposing movement of the same. The force exerted by the spring biasing increases as the armature is moved to attracted or operative position so that largest portion ofthe tractive force exerted by the electromagnet in moving the armature to attracted position is used up in overcoming the resistance'of the spring biasing means. Thus onlya relatively small portion of the force exertedby the electromagnet is available for performing thework involved in moving the latch means and /or the trip bar to tripping position. This condition becomes even a greater problem in the case of shock-proof circuit breakers because in such breakers even stronger springs must be used to bias both the latch and /or trip bar, and the armature to their normal positions in order to prevent these elements from being moved to tripthe breaker by jarring forces or vibrations. 1 i

It is accordingly an object of my invention to provide an improved trip device for a circuit breaker in which a maximum portion of the overload tripping force exerted on the trip actuating member is rendered available to perform the work involved in tripping the breaker.

Another object of my invention is to provide an improved shock-proof trip device for a circuit breaker.

Another object or invention is to provide a tripdevice for a circuit breaker with a novel and improved means for restraining the trip actuating member of the trip device in its normal or inoperative position. I

Another object ofmy invention is to provide an improved trip device for a circuit breaker, in which the trip actuating member is rendered 1937, Serial No. 124,253. (01. 200-106) shock proof and in which a maximum amount of the tripping force exerted on said actuating member is rendered available to perform the work involved in tripping thebreaker. 7

Another object of my invention is to provide an electromagnetic trip device for a circuit breaker embodying a trip actuating armature with a novel means for restraining the armature in normal or inoperative position to render the same substantially shock proof, in which the restraining force decreases rapidly as the armature moves toward attracted position whereby a maximum portion of the tripping force exerted on the armature is rendered available to perform the work involved in tripping the breaker.

The novel features that I consider characteristic of my invention are set forth in particular in the appended claims, the invention itself, however, both as to structure and operation, together with additional objects and advantages titer-bi will best be understood from the following detaileddescription of a specific embodiment thereof when read in connection with the accompanying drawings, in which I Figure l is a plan view of' the circuit breaker embodying the features 'of my invention, the cover of the circuit breaker having been removed.

Fig. 2 is a vertical sectional view of the circuit breaker shown in Fig. 1, taken on the line II-II I thereof and looking in the direction of the arrows, the cover being shown in mounted position.

Fig. 3 is a vertical sectional view of the trip device of the circuit breaker taken on the line III-J1]: of Fig. 5. r

Fig. 4 is a vertical sectional view of the trip device of the circuit'breaker taken on the line IV-IV of Fig. 5.

Fig. 5 is an elevational view of the trip de vice.

Fig. 6 is aforce-distance curve showing the work available for tripping the breaker when relatively strong springs are used for biasing the armature to attractecl'position, and I Fig. 7 is a similar force-distance curve showing the work available for tripping the same breaker whenthe trip device embodying thefeatures of my invention is used.

The invention has been shown in connection with a particular form of multi-pole circuit breaker for illustrative purposes only. It will be understood, however, from the following description that the invention is capable of more or 1655 general application to various other forms of circult controlling devices and electrical devices.

Since the invention is particularly concerned with the electro-responsive trip device and since the circuit breaker wherein my invention has been embodied is completely described in the copending application of Harry J. Lingal, Serial No. 637,749, filed October 14, 1932, and assigned to the assignee of this invention, which became Patent No. 2,083,305 on June 8, 1937, the description of the breaker will be limited to setting forth the various elements. It will be noted that the reference numerals for this case coincide with the reference numerals for Serial No. 637,749. This has been done to facilitate a comparison thereof.

Referring to the drawings, the base I is of molded insulating material and has mounted thereon terminal contacts 3 and 5, the removable unitary trip device 1, the circuit breaker operating mechanism 9 which has associated therewith the assemblage of the switch members II, the arc extinguishers I3, and the stationary. contact assemblages I5 of the switch members. The assemblage of the switch members II and the stationary contact assemblages I5 combine to form a plurality of poles. Each of the poles is insulated from the adjacent pole by means of insulating barriers II (Figs. 1 and 2) which are molded into the base I. These insulating barriers II are adapted to align with similar shaped barriers 2| molded in the cover I9 which is likewise of insulating material. The operating member 23 has a removable handle 25 and is pivoted to the main frame 4| of the operating mechanism 9. An opening 21 is provided in the cover I9 to accommodate the operating handle. The trip device I is mounted in position by the screw fastenings 3| and 33 which also serve to electrically connect the terminals 35 and 31 of the trip device with the laminated shunts 39 and the terminals 5 respectively.

The electrical circuit for each of the poles is substantially the same. Beginning with the terminal 3, the current passes successively along the arc extinguishing structure I3, thence through the main stationary contact I8, the cooperating main moving contact I8 and the flexible shunt 39 which is associated with each of the switch members, the terminal 35 of the trip structure I, and finally through the trip structure to the other terminal 5.

The assemblage of the switch members II is pivoted to the main frame 4| of the operating mechanism 9 by means of a pin 42. A steel tie bar 43 serves to rigidly mechanically interconnect the three switch members II, there being only one pivot point. Each of the switch members II includes a clamp member 45 for engaging the tie bar 43. The clamp members are secured to the tie bar by means of bolts 41 or any other suitable form of securing means. A square tube 48 of insulating material is'disposed between the tie bar 43 and the clamping members 45 to insulate the several poles of the braker from each other. The main moving contacts I8 3 are pivoted to the clamp members 45 through of rivets 51. Each of the mainmoving contact members I8 has a rearwardly extending portion 59 for engaging the end of the shunt 39 and for defining the limit of movement of each of the contact members I8 under the biasing action of the contact springs 55. The shunts 39 for the two outer poles are rigidly aflixed to the base I by means of screw fastenings GI and 64 which pass through suitable openings in the shunts. The shunt 39 for the central pole is held in place by four screws 62 which engage threaded openings in the base of the main frame 4|. The shunts 39 are of laminated construction being built up of a plurality of thin sheets of copper. The clamp member 45 of the central switch member has openings 86 for engaging the contact assemblage pivot pin 42, openings 61 for engaging the breaker operating mechanism, and slotted openings 69 for clearing the pivot pin I5 of the main operating member 23.

Any suitable type of arc extinguishing means may be used. The form illustrated is similar to those shown in Patent No. 1,896,764 of M. W. Brainard issued February 7, 1933, and assigned to the assignee of this invention.

The operating mechanism 9 comprises in general a base or main frame 4|, a pair of toggle links 71 and 19, one end of which is connected to the assemblage of switch members I I through the central clamp member 45, a carrier lever 8| for releasably restraining the other end of the toggle links I1 and I9 in operative position, an operating member 23, an overcenter spring unit 83 for connecting the operating member 23 to the knee of the toggle links, and the operating handle 25.

The base 4| is positioned above the conducting shunt 39 of the central pole and is rigidly aflixed to the base by means of the screw 62. One

end of the toggle link 11 operatively engages the openings 61 in the central clamping member 45 through the agency of a pivot pin 89. The other end of the toggle link 71 is pivoted to one end of the toggle link I9 by means of a knee pivot pin 9|, the toggle links 11 and I9 are provided with portions which engage when the breaker is in the closed position to define the limit of upward movement of the knee of the toggle.

The overcenter spring unit 83 operatively connects the end 95 of the operating member 23 with the knee pivot pin 9| of the toggle links and exerts a tension force therebetween. The overcenter spring unit 93 comprises a frame 96 one end of which is adapted to engage the knee pivot pin 9| and the other end of which has a circular opening to accommodate the plunger member 91. The overcenter spring 98 which is itself in compression is positioned between the end'of the frame 96 and the enlarged portion 99 of the plunger 91. The outer end of the plunger 91 pivotally engages the end 95 of the operating member 23 by means of a pin |0| which fits in a suitable recess I02.

The end I03 of the toggle link I9 is provided with a circular bearing portion I04 which engages a suitable recess in the end of the bell crank carrier lever 8|. Two retaining plates I05 are disposed on the outer sides of the carrier 8| to prevent the bearing portion I04 from moving sideways and disengaging the recess.

The bell crank carrier lever 8| has a projecting portion I0I for engaging the latching lever III and is pivoted to the base 4| at its apex by means of a pivot pin I09. The portion 0 of the carrier 8| extends along the base 4| to form what might be termed a tail portion. The perpendicular distance from the center of the carrier pivot pin I G9 to the line of action of the toggle lever 19 is considerably less than the distance from the center point of the carrier pivot pin I09 to the projecting portion I01 of the carrier 8|. This gives the carrier lever 8| an appreciable mechanical advantage over the toggle.

The overcenter spring unit 83 at all times exerts a force on the carrier lever 8| biasing the lever in a clockwise direction and it is to restrain the carrier lever in the operative position that the latching lever I I I is provided.

The latching lever III includes a projecting portion IIZ for engaging the end of the section I01 of the carrier lever BI, and a portion H3 for engaging the trip latch I (see Fig. 4). One end of the latching lever III is pivoted to the base 4| by the pivot pin II5 adjacent the point of engagement with the tail piece III! of the carrier member 5|. The projecting portion II2 of the latching lever normally overhangs the end of the portion I01 oi the carrier lever BI and thus holds the carrier in an operative position by preventing it from moving upward. The free end of the latching lever III is releasably restrained in the position shown in Fig. 2 by reason of the engagement of the portion I13 with the trip latch I59, which latter forms a part of the trip device 1.

The trip device is of the same general type as that disclosed and claimed in the copending application of Jerome Sandin, Serial No. 123,236, filed January 30, 193'7'and assigned to the as signee of this invention; now Patent 2,178,083 issued October 31. 1939. The trip structure 1 is a unitary device entirely assembled upon its own base I53 of molded insulating material and is completely removable from the breaker; the screw fastenings 3| and 33 being utilized to mount the trip structure on the base I and to also make the necessary electrical connections. The trip device 1 includes a magnetically responsive element for each of the poles, and the mechanism of the device is so arranged that a heavy overload in the circuit controlled by any one of the poles will actuate the trip mechanism instantaneously to open all of the poles of the breaker.

Each of the trip elements of the trip device are mounted on the trip base I 53 through the agency of a metallic yoke I553. The yoke I is substantially U-shaped and has a pair of outstanding lugs I51 for pivotally supporting a U-shaped armature I59. The armature I59 is pivotally mounted on the lugs I51 by means of pivot pins I6I. Each of the. legs of the yoke I55 is provided with an offset angular end portion I55, for supporting a transverse stationary core member I 55. The stationary core member IE5 is secured to the onset ends I53 of the yoke by means of screw fastenings I61. Each of the armatures I59 is adapted to be biasedtoward its normal position; as shown in Figs. 3 and 4,. by means of a pair of relatively light biasing springs IE9. The. springs I69 are disposed upon studs I?! which are carried by the base I53 of the trip device. One end of each of the springs I59 engages a slidable bushing I13 which is slid'ably mounted on the stud I1! and the other end of each spring is held in stressed condition by means of a washer I15 and a cotter pin I11. The force exerted by the springs I69 causes the slidable bushings I13 to engage and bias the armatures I59 to their normal position, as shown in Figs. 3 and 4. An energizing conductor I19 is provided for each of the trip elements. The ends of the conductors form the terminals 35 and 31 of each trip device, and the body portion passes between the legs of the arma ture I59 and the yoke I55. The energizing conductor I19 and the stationary core I form an electromagnetic means for attracting and moving the movable armature I59 to an attracted position against the stationary core I65. The cross piece IBI of non-magnetic material is secured to the ends of the legs of each of the armatures I59 in order to provide a balancing means for the armature so as to render the same less responsive to movement by shock or jarring forces.

In order to provide for accurate positioning of the trip device with respect to the path of movement of the latching lever I I I, there is provided a metallic bracket I53 which is rigidly affixed to the center portion of the trip base I53 by means of screw fastenings (not shown). The bracket I83 has a base portion I85 which is of substantially the same outline as the center terminal 35 and is thus adapted to be fastened to the base of the circuit breaker by means of the screw fastenings 3| of the central pole. The central fastenings 3| would probably be suflicient to accurately position the trip device but in order to insure that the position is correct, there is provided an additional positioning means which consists of a pro- I jecting male member I81 which extends downwardly (Fig. 4) through a suitable opening in the center terminal 35 and is adapted to engage a cooperating female portion I89 in the center shunt 3.9; this shunt being securely fastened to the base I and accurately positioned With respect to the operating mechanism by means of the screw fastenings 62.

The bracket I85 has an opening I9! in the upper portion, the trip lever I58 being pivotally mounted therein through the. agency of a pivot pin I93.

The trip lever I58 is preferably constructed of metal and has a projecting portion I for engaging the latch engaging means associated with the latching lever I I I. A spring I91 is provided for biasing the trip lever I 59 to the latched posi tion, and a notch I99 is provided in the trip lever for engaging the trip bar 2c I.

The trip bar ROI is of molded insulating material and extends. across all three poles of the breaker. It is pivotally supported at two points adjacent and. on either side of the trip lever I59 by means of a pair of lugs 293 which. project from the base I53 of the trip device. Lugs 253 are provided with openings for the reception of pivot pins 205 carried by the trip bar. Filler screws 261 are provided for maintaining the trip bar in pivotally mounted position. The trip bar 29I engages the trip lever I5iI through the agency of a bracket 299, one end of which engages the notch I99 and the other end of which is rigidly affixed to the trip bar by a pair of rivets. compression spring 2H biases the trip bar clockwise (Fig. 4) about its pivot axis to its latched posi tion. Three downwardly extending members ZI-Z-i each aflixed to the trip bar by means of a rivet are provided for engagement by the armatures I555 or" each of the magnetically responsive elements of the trip device. A cover 2I5 is positioned'on the trip base in order to protect and enclose the various elements of the trip device.

The portion II3 of the latching lever II I includes a bifurcated projection 2I1 which pivotally supports a latch engaging lever 2I9 through the agency of a pivot pin 22I. The latch engaging lever 2I9 is biased into engaging position by a spring 223 and its movement in a clockwise direction is limited by the base portion of the bifurcated projection 2I1.

The trip bar MI and the members carried thereby are so constructed that the trip bar is both statically and dynamically balanced in order to render the same substantially shock proof. The positioning of the pivot means of the trip bar on either side of and adjacent the latch load prevents any flexing of the trip bar which would tend to throw the same out of balance.

In the type of trip device disclosed in the copending application of Jerome Sandin, Serial No. 123,236, referred to above, relatively strong biasing springs are used for biasing the armatures to their normal position in order to render the same substantially shock proof. While this arrangement has the advantage of rendering the armatures substantially shock proof so that they will not be moved by a jarring force to cause tripping of the breaker, an inherent disadvantage is present. When the springs are made relatively strong, substantially the greatest portion of the force exerted by the electromagnetic means including the energizing conductor and the stationary core is absorbed or used up in overcoming the resistance of the relatively strong biasing springs and only a small portion of the force is rendered available for'performing the work necessary to move the latches and trip the breaker.

By my invention, I have provided a biasing means for the armature which renders the same substantially shock proof and at the same time permits a maximum portion of the force exerted by the electromagnetic means to be rendered available for the purpose of performing the work necessary to trip the breaker. To accomplish the above stated function, the springs I69 are constructed of relatively fine wire with a large number of turns so that these springs exert a relatively small biasing force sufficient to return the armature to normal position following deenergization of the electromagnetic means after the same has moved the armature to its attracted position. In combination with the relatively light springs I69, a stationary plate 225 of magnetic material is mounted on the yoke I55 of each of the electro-responsive trip elements. The armature I59 is provided with a small air gap or a small insert of non-magnetic material 221 adjacent the plate 225 as shown in Fig. 5. When the circuit breaker is closed the current flowing through the energizing conductor I19 produces a circular magnetic field about the conductor I19 which in turn produces a magnetic flux in the armature I59 and the core I65. The flux produced would ordinarily, without the presence of the plate 225 and the gap 221, flow through the armature I59 and core I65 and across the air gaps between the ends of the armature I 59 and the core I65. The gap 221, however, shunts a portion of the magnetic flux through the plate 225. The flux thus produced in the plate 225 creates a magnetic attracting force between the armature I 59 and the plate 225 which acts to restrain the armature in its normal position, shown in Figs. 3 and 4, with a predetermined force. The plates 225 are dimensioned so as to become saturated at normal current values or at current values slightly above normal so that the attractive force between the plates and the arma tures becomes a maximum at such current values. This attractive or restraining force is sufiicient to prevent the armatures I59 from being moved towardv attracted position in response to jarring toward attracted position.

forces or heavy vibrations applied to the base of the braker. If a heavy magnitude overload occurs, the flux produced in the armature I59 and the stationary core I65 becomes sufficient to move the armature to its attracted position. As the armature is moved toward attracted position, the restraining flux force exerted between the plate 225 and the armature I59 decreases rapidly and becomes substantially zero after the armature has been moved a small portion of the distance After the armature has moved a small portion of the distance toward attracted position, the only restraining force tending to prevent movement of the armature is the small force exerted by the relatively weak springs I69 so that a maximum portion of the pull of the electromagnetic means is rendered available for the purpose of overcoming the latch load of the circuit breaker.

Fig. 6 illustrates a force-distance curve for a circuit breaker which does not embody the features of my invention but which utilizes relatively strong springs for biasing the armature to its normal position. The contour A represents the trip force produced by the magnetic flux during an overload. The contour B represents the resisting force produced by the relatively strong biasing springs. I represents the initial or normal position of the movable armature and F represents the final or trip position of the movable armature. L represents the travel of the movable armature or the air gap between the movable armature and the stationary core. The area W1 represents the work available to release the trigger and Y represents the trip force necessary to start movement of the armature. It will be noted from Fig. 6 that a relatively small amount of Work represented by the area W1 is available for actually performing the work of tripping the breaker because of the fact that a large portion of the force produced by the magnetic flux is used up in overcoming the resistance of the strong biasing springs.

Fig. '7 illustrates a force-distance curve with a circuit breaker when the same is equipped with a trip device embodying the features of my invention. Referring to Fig. 7, the contour A1 represents the trip force produced by the magnetic flux on overload and is the same as in Fig. 6. The contour represents the force exerted by the relatively weak springs I69 which bias the armature toward its normal position. The contour D represents the restraining force produced by the magnetic flux between the magnetic plate 225 and the armature I 59. The contour B1 is the sum. of C and D and shows the combined force produced by the relatively weak biasing springs I69 and the flux force produced by the magnetic plate 225. The area. W2 represents the work available for overcoming the latch load of the circuit breaker. The point I represents the initial or normal position of the armatureand the point F represents the final or tripped position of the movable armature. L represents the travel of the movable armature or the air gap between the armature I59 and the stationary core I65. Y represents the 'trip force necessary to start moving the armature. It will be noted from Fig. 7 that a considerably larger amount of work is rendered available for actually tripping the breaker (represented by the area W2) when a trip device embodying the features of my invention is used, than in the case of a trip device embodying relatively strong biasing terclockwise (Fig. 2) about its pivot pin l core Hi5 and armature springs for biasing the armature to normal positionand rendering the same shock proof.

The exact details of operation of the, circuit breaker mechanism 53 are setrorth in the previously mentioned application otH-arry J. Lingal and the disposition of the various parts of the mechanism in. the open, closed and the tripped position are shown in the drawings accompanying that. application. Generally however, the operation is follows. To. manually move the contacts from the closed position shown 2 to the openposition, the handle 25 is moved downwardly. This downward movement causes the toggle links l? and it to collapse toward the base I under the influence oi neovcrccnter spring unit 83. The collapse of the toggle causes the entire. assemblage ofthe switch members H to pivot about the pin 42 and move to open position with a snap action. To close the con-- tacts manually, the operation is'reversed, the handle 25 is moved upwardlyand the toggle is restored to the position, shown: in Fig. 2 by the force exerted by the ,overcenter spring unit. The contacts, close as well as open with a snap action due to the progressive acceleration given the toggle. v

When the circuit breaker isin. the closed circuit position (Fig. 2) and an'overload. ofsuiilcient. magnitude .to actuate the trip device ocours in the circuit controlled by any one of poles of the breaker; th latching leverlto released by the movement of trip bar .ltil t effect release of the free end of the etching lever Hi. The latching lever ill is biased couniii, and assoon as it is released itmoves so that the portion H2 thereof uncovers the cooperating end portion it? of the. tail member 2 so of the carrier lever M. The entire mechanism is now free to move under the biasing action of the contact springs 55. These springs cause the assemblage of the switch members to move counterclockwise about the pivot pin 62, and at the same time cause the toggle links llto be moved toward the base of the circuit breaker. The combined res of these movements is to cause a clockwise me a ment of the carrier lever 32 a col toggle links toward the base i due to l bringing ofthe center line of the overcenter spring unit 83 below the center line of the toggle link. i The circuit breaker operating mechanismis com pletely resettableby means associated with the operating member 23.

The operation of the trip device is substantially as follows. Upon the occurrence of overload in the circuit controlled by any one or the poles of the breaker, the energizationof the stationary its reach s a suffi'cient magnituce to overcome the restraining force exerted on the movable armature by the magnetic plate 225 and the biasing springs i559, and to move the armature $53 to its attracted posi tion. The movement of the armature N29 to its I attracted position toward the stationary core it?) causes the, armature to engage the downwardly extending member t3 and move the same so as to cause counterclockwise rotation. of the trip bar 29!. The counterclockwise rotation of the trip bar 2% causes the bracket carried thereby to release the latch lever 55! thus permitting the. latch. engaging lever are amxed to the free end. of the latching lever ill to disengage the projection I95 on the latch lever I555. The free end of thelatching lever l I l is biased away from the: base. by the. operating mechanism; itseli. and

it, therefore, immediately moves to the tripped position thereby causing the contacts or" the breaker to open. As soon as the latch engaging lever M9 has disengaged the projection H95 on the latch 950, the biasing spring 291 restores the latch Hill to latched position shown in Fig. i.

The provision of magnetic plate 225 for restraining the armature 59 in its normal position with a predetermined force renders the armature substantially shock proof so that any tendcncy of the same to be moved by a jarring force or vibration is prevented. The provision of the gnetic plate 225 also permits the use of relavely weal: biasing springs it?) for biasing the or nature toward its normal position and sinceshock proof, it is to be understood that the principles of my invention are applicable to other forms of trip devices, circuit interrupter-s, or electrical devices, r

I have given the foregoing details of a practical embodiment of my invention in accordance with the patent statutes. It is to be understood, however, that various changes in the structure may be made without departing from the spirit of my invention. I desire, therefore, that the invention be limited onlyby the reasonable construeticn of the appended claims and by the prior art.

I claim as my invention: I

1. In a circuit breaker having relatively movable contacts, operating mechanism for opening and for closing said contacts, and spring-biased actuating member releasable to effect opening of said contacts; a trip device comprising releasable latch means for restraining said.- actuating member, an armature movable from a normal unattracted position to an attracted position to efiect release of said latch means to free said actuating member, an. electromagnet connected in. circuit with said contacts operable in response to overload currents of more than predetermined magnitude to move armature to attracted position, and means including member I of magnetic material positioned adjacent armature in its normal position. for rest-raining said armature in its normal position with a predetermined iorce, said armature having a portion of increased reluctance adjacent said men.- ber of magnetic material for causing portion of the magnetic flux to be shunted through said member, and said member being arranged to become saturated at a current below said prodeter mined magnitude, whereby said armature is rendered substantially shock proof, and whereby a large portion of the to co exerted by said electromagnetic means on overload becomes available for effecting release of said latch means during movement of said armature to tripping position.

2. n a circuit breaker having relatively movable contacts, operating mechanism for opening and for closing said contacts, and a spring biased actuating member releasable to efiect opening of said contacts; a trip device comprising releasable holdingv means for restrainingsaicl actuating member, an armature movable from a normal position to an attracted position to efiect release of said holding means, an electromagnet connected in circuit with said contacts operable in response to predetermined overload conditions to move said armature to attracted position to effect release of said holding means to free said actuating member, a member of magnetic material disposed adjacent said armature in its normal position for restraining said armature in its normal position with a predetermined force, said armature being provided with a gap adjacent said member so that a portion of the flux produced in said armature is shunted around the gap by said member, said member being constructed so as to become saturated at normal current values.

3. In a circuit breaker having relatively movable contacts, operating mechanism for opening and for closing said contacts, and a spring biased actuating member releasable to effect opening of said contacts; a trip device comprising releasable holding means for normally restraining said actuating member, electromagnetic means including a pivoted armature movable from a normal position to an attracted position to effect release of said holding means to free said actuating member, a core of magnetic material and an energizing winding connected in circuit with said contacts operable in response to predetermined overload conditions to move said armature to attracted position, a member of magnetic material disposed adjacent said armature in its attracted position arranged to become saturated at normal current value, said armature having a portion of greater reluctance adjacent said member for causing a portion of the magnetic flux to be shunted through said member, said member restraining said armature in its normal position with a predetermined force to render the same substantially shock proof; and relatively light springs for biasing said armature to normal position.

4. A control device for electrical apparatus comprising an armature movable from a normal position to an attracted position to operate said apparatus, electromagnetic means for said armature operable in response to currents of more than a predetermined magnitude to move said armature to attracted position, and a member of magnetic material positioned adjacent said armature in its normal position, said armature having a portion of greater reluctance adjacent said member for causing a portion of the magnetic flux to be shunted through said member, and said member being arranged to become saturated at a current value below said predetermined magnitude, whereby said member restrains said armature in its normal position with a predetermined force.

5. A trip device for a circuit breaker comprising an armature movable from a normal position to an attracted position to effect tripping of said breaker, electromagnetic means for said armature energized by the-circuit controlled by the breaker and operable in response to predetermined abnormal conditions to move said armature to attracted position, a member of magnetic material mounted adjacent said armature in its normal position said armature being provided with a portion of non-magnetic material adjacent said member so that said member shunts a portion of the flux produced in said armature, said member being arranged to become saturated at normal current values whereby it restrains said armature in its normal position with a predetermined force; and relatively weak spring means for biasing said armature to its normal position.

6. A trip device for a circuit breaker comprising an armature movable from a normal position to an attracted position to effect tripping of said breaker, electromagnetic means for said armature energized by the circuit controlled by the breaker and operable in response to predetermined abnormal conditions to move said armature to attracted position, a member of magnetic material mounted adjacent said armature in its normal position, said armature being provided with a gap adjacent said member so that said member shunts a portion of the flux produced in said armature, said member being arranged to become saturated at normal curent values whereby it restrains said armature in its normal position with a predetermined force.

7. In a circuit interrupter having relatively movable contacts, electromagnetic trip means operable in response to predetermined conditions to cause opening of said contacts comprising a core of magnetic material and a movable annature forming a substantially closed magnetic circuit having at least one air gap between the armature and the core when the armature is in normal unattracted position, and an energizing conductor connected in circuit with said contacts, said armature being movable from a normal unattracted position to an attracted position in response to predetermined condiitons to cause opening of said contacts, and a member of magnetic material mounted adjacent said armature and included in the magnetic circuit when the armature is in its normal position for restraining said armature in its normal position with a predetermined force, said armature having a portion of increased reluctance adjacent said member for causing a portion of the magnetic flux to be shunted through said member.

8. In a circuit breaker, relatively movable contacts biased to open circuit position, releasable latch means for latching said contacts in closed circuit position, electromagnetic trip means comprising a core of magnetic material and a movable armature of magnetic material forming a substantially closed magnetic circuit having at least one air gap between the armature and core when the armature is in normal unattracted position, and an energizing conductor connected in circuit with said contacts, said armature being movable from its normal position to an attracted position in response to predetermined conditions to effect release of said latch means and opening of said contacts, and a member of magnetic material mounted adjacent said armature and included in the magnetic circuit when the armature is in its normal position for restraining said armature in its normal position with a predetermined force to prevent said armature from being moved to attracted position by shocks or jar ring forces, said armature having a portion of increased reluctance adjacent said member for causing a portion of the magnetic flux to be shunted through said member.

9. In a circuit breaker relatively movable contact means, operating means for opening and closing said contacts including a spring biased actuating member releasable to cause opening of I said contacts, electromagnetic trip means operable in response to predetermined conditions to release said actuating member to cause opening 01 said contacts comprising a a core of magnetic material and a movable armature forming a substantially closed magnetic circuit having at least one air gap between the armature and the core when the armature is in normal unattracted position, and an energizing conductor connected in circuit with said contacts, said armature being movable to an attracted position to efiect release of said actuating member, and means including a member of magnetic material mounted adjacent said armature and included in the magnetic circuit when the armature is in its normal position for restraining said armature in its normal position with a force sufiicient to prevent said armature from being moved to attracted position by shocks or jarring forces, said armature having a portion of greater reluctance adjacent said member of magnetic material for causing a portion of the magnetic flux to be shunted through said member, the restraining force exerted by said member of magnetic material decreasing rapidly as said armature is moved toward attracted position in response to said predetermined conditions whereby a large portionof the force exerted by said electromagnetic means becomes available for tripping the breaker during movement of said armature toward attracted position,

10. An electromagnetic trip device for a circuit breaker comprising a core of magnetic material and a movable armature of magnetic material forming a substantially closed magnetic circuit having at least one air gap between the armature and the core when the armature is in normal unattracted position, said armature being movable from its normal position to an attracted position in response to predetermined conditions to trip said breaker, and a member of magnetic material mounted adjacent said armature and included in the magnetic circuit when the armature is in its normal position for restraining said armature in its normal position with a predetermined force, said armature having a portion of greater reluctance adjacent said member of magnetic material for causing a portion of the magnetic flux to be shunted through said member.

11. An electromagnetic trip device for a circuit breaker comprising a core of magnetic material and a movable armature of magnetic material forming a substantially closed magnetic circuit having at least one air gap between the armature and the core when the armature is in normal unattracted position, said armature being movable from its normal position to an attracted position in response to predetermined conditions to trip said breaker, and a member of magnetic material mounted adjacent said armature and included in the magnetic circuit when the armature is in its normal position for restraining said armature in its normal position with a predetermined force sufiicient to prevent said armature from being moved toward attracted position to falsely trip said breaker by shocks or jarring forces, said armature having a portion of greater reluctance adjacent said member of magneticmaterial for causing a portion of the magnetic flux to be shunted through said member; and relatively weak spring means biasing said armature to its normal position.

12. An electromagnetic trip device for a circuit breaker comprising a core of magnetic material and a movable armature of magnetic material forming a substantially closed magnetic circuit having at least one air gap between the armature and the core when the armature is in normal unattracted position, said armature being movable from its normal position to an attracted position in response to predetermined conditions to trip said breaker, a member of magnetic material mounted adjacent said armature, said armature being provided with a gap adjacent said member so that a portion of the magnetic flux produced in said armature is shunted through said magnetic member to cause said member to restrain said armature in its normal position with a predetermined force.

13. An electromagnetic trip device for a circuit breaker comprising a U shaped movable armature and a core of magnetic material mounted adjacent the ends of said armature forming a substantially closed magnetic circuit, an energizing conductor threading said core and armature, said armature being movable from a normal position to an attracted position in response to predetermined conditions to trip said breaker, and a member of magnetic material mounted adjacent said armature and included in the magnetic circuit when the armature is in its normal position for restraining said armature in its normal position with a predetermined force, said armature having a portion of greater reluctance adjacent said member of magnetic material for causing a portion ,of the magnetic flux to be shunted through said member.

TURE LINDSTROM. 

